Skin melanocytes: biology and development

Abstract

In the human skin, melanocytes are present in the epidermis and hair follicles. The basic features of these cells are the ability to melanin production and the origin from neural crest cells. This last element is important because there are other cells able to produce melanin but of different embryonic origin (pigmented epithelium of retina, some neurons, adipocytes). The life cycle of melanocyte consists of several steps including differentiation of melanocyte lineage/s from neural crest, migration and proliferation of melanoblasts, differentiation of melanoblasts into melanocytes, proliferation and maturation of melanocytes at the target places (activity of melanogenic enzymes, melanosome formation and transport to keratinocytes) and eventual cell death (hair melanocytes). Melanocytes of the epidermis and hair are cells sharing some common features but in general they form biologically different populations living in unique niches of the skin.

Insights into the biological functions of Dock family guanine nucleotide exchange factors

“…Two independent spontaneous mouse mutant lines, misty and moonlight (Table 1), were identified due to a hypopigmented and white-spotted phenotype resulting from genomic deletions in the Dock7 locus (Blasius et al 2009). Surprisingly, the cellular and molecular bases for the hypopigmentation have not yet been addressed in these models; an attractive hypothesis would be that Dock7 is required for melanocyte progenitor differentiation or their migration from the neural crest to the ectoderm (Cichorek et al 2013).…”

Observing and Understanding the Ultrafast Photochemistry in Small Molecules: Applications to Sunscreens

“…The primary melanins are eumelanin, a blackbrown pigment and pheomelanin, a yellow-reddish pigment, both of which are synthesised inside specialised cells called melanocytes 10 . Melanocytes are distributed throughout the skin, predominately in the stratum basale layer, see Figure 1(A).…”

Photoprotection: extending lessons learned from studying natural sunscreens to the design of artificial sunscreen constituents

“…3 shows, specialised cells termed melanocytes are distributed throughout the stratum basale layer. 30 These synthesise vesicles termed melanosomes which, in turn, synthesise melanin. 30,31 Melanocytes form long projections (dendrites) out to surrounding skin keratinocytes (the dominant cell type in the epidermis) in the stratum basale and stratum spinosum layers; typically, one melanocyte reaches upwards of 40 keratinocytes.…”

“…The overall photoprotection provided will depend on the concentration and distribution of melanocytes, and their size and morphology, as well as the concentration of melanin inside the melanosomes -properties which are regulated by a set of genes via processes collectively known as melanogenesis. 25,30,34 Melanogenesis turns a static picture of photoprotection into a dynamic, adaptive, photoprotective process. For example, when skin is subjected to high levels of UVR, against which the current level of skin pigmentation offers insufficient protection, signalling pathways up-regulate melanogenesis, thereby increasing the number of melanocytes and melanosome production, causing facultative skin colour (tanning).…”